The role of CT Thorax scans in triaging suspected cases of Covid-19

Abstract

Covid-19 is an infectious disease caused by SARS-CoV-2. Prior to the introduction of SAMBA II RT-PCR, swab results would take up to 24 hours. The RT-PCR assays have a sensitivity of 71-98% (Watson, J. et al. BMJ 2020; 369:m1808). The aim of this study was to determine the clinical accuracy of using non-contrast CT Thorax scanning as a method of diagnosing and triaging patients to appropriate Covid-19 or non-Covid-19 wards from the Emergency Department.

A retrospective cohort study was conducted on consecutive patients who were admitted between 26th June and 31st July 2020 in a local District General Hospital in the United Kingdom. All radiological findings were compared with serial RT-PCR and antibody (Ab) testing, clinical symptoms, and relevant laboratory parameters.

Of 85 patients that met the eligibility criteria, 26 cases (30.6%) demonstrated radiological features consistent with Covid-19, with two (7.7%) of these being confirmed positive for Covid-19 within two weeks of admission. Eight patients tested positive for Covid-19 Abs on admission, half of which were positively correlated to CT findings. The patients who had no radiological features of Covid-19 on CT did not receive a laboratory, clinical or epidemiological diagnosis of Covid-19. Overall 41 patients had acute lymphopenia (48.2%), with 16 of these patients having a suspicious CT for Covid-19.

Analysis of our cohort of patients showed that a CT Thorax can be an important adjunct to diagnose Covid-19 in patients who swab negative. Our data also supports its use in select situations to triage patients to appropriate wards, where there is clinical and microbiological diagnostic uncertainty. However, radiation exposure to the patient must be considered.